1. Field of the Invention
Embodiments of the present invention generally relate to a method and system for testing substrates. More particularly, the embodiments relate to a method of testing and system for testing large area substrates in the production of flat panel displays.
2. Description of the Related Art
Flat panel displays, such as, for example active matrix liquid crystal displays (LCD's), have recently become commonplace in the world as a replacement for the cathode ray tubes of the past. A LCD has several advantages over the CRT, including higher picture quality, lighter weight, lower voltage requirements, and low power consumption. The displays have many applications in computer monitors, cell phones and televisions to name but a few.
A part of the LCD manufacturing process requires testing of the flat panel substrate to determine the operability of pixels. Voltage imaging, charge sensing, and electron beam testing are some processes used to monitor and troubleshoot defects during the manufacturing process. In a typical electron beam testing process, the response of the pixels is monitored to provide defect information. In one example of electron beam testing, certain voltages are applied to the pixels, and an electron beam may be directed to the individual pixel electrodes under investigation. Secondary electrons emitted from the pixel electrode area are sensed to determine the TFT voltages.
The demand for larger displays, increased production, and lower manufacturing costs has created a need for new testing systems that can accommodate larger substrate sizes using minimal clean room space. Current flat panel display processing equipment generally accommodates large area substrates up to about 2200 mm by 2500 mm and larger. The size of the processing equipment as well as process throughput time is a great concern to flat panel display manufacturers, both from a financial standpoint and a design standpoint.
To meet this challenge, test systems have been developed wherein the testing chamber is slightly larger than a width or a length of the large area substrate in one dimension and the substrate is processed in at least one linear direction during testing. This unidirectional movement may require one or more electron beam columns, and the columns' respective address area, to be in closer proximity, thereby creating the possibility of cross-talk between adjacent columns. This cross-talk may produce testing challenges if not reduced or eliminated.
Therefore, there is a need for a test system to perform testing on large area substrates that minimizes clean room space and reduces testing time, and a method of reducing cross-talk between the address areas of the testing apparatus.